A mobile crane usually comprises not only a combustion engine in the undercarriage, which is provided for the traction drive, but also another combustion engine in the superstructure which is provided exclusively for supplying power to the consumers in the superstructure, such as for example the lifting mechanism, the derricking mechanism or the telescoping mechanism.
In smaller mobile cranes, and in recent years increasingly in larger mobile cranes as well, there has been a switch, in favour of lower inherent weight and the associated advantages, towards using the undercarriage motor—originally used mainly for the traction drive—for supplying power to the crane superstructure as well. One known design solution envisages a hydraulic pump in the crane undercarriage for this purpose, which is driven by the undercarriage motor and in turn drives a hydraulic motor via a hydraulic circuit which extends from the undercarriage into the superstructure. The individual pumps for the respective crane functions are coupled to and driven by said hydraulic motor. Said pumps are dimensioned in accordance with their respective power requirements and therefore reach their optimum operating point at different rotary speeds. Consequently, a so-called pump transfer gearbox has to be connected downstream of the motor, via which the individual pumps are coupled to the hydraulic motor at a rotary speed which is optimised for them. However, this pump transfer gearbox itself incurs an increased weight and cost outlay.